Viral oncolysis

Mesenchymal stem cell-released oncolytic virus: an innovative strategy for cancer treatment

Oncolytic viruses (OVs) infect, multiply, and finally remove tumor cells selectively, causing no damage to normal cells in the process. Because of their specific features, such as, the ability to induce immunogenic cell death and to contain curative transgenes in their genomes, OVs have attracted attention as candidates to be utilized in cooperation with immunotherapies for cancer treatment. This treatment takes advantage of most tumor cells' inherent tendency to be infected by certain OVs and both innate and adaptive immune responses are elicited by OV infection and oncolysis. OVs can also modulate tumor microenvironment and boost anti-tumor immune responses. Mesenchymal stem cells (MSC) are gathering interest as promising anti-cancer treatments with the ability to address a wide range of cancers. MSCs exhibit tumor-trophic migration characteristics, allowing them to be used as delivery vehicles for successful, targeted treatment of isolated tumors and metastatic malignancies. Preclinical and clinical research were reviewed in this study to discuss using MSC-released OVs as a novel method for the treatment of cancer. Video Abstract.

Preexisting immunity: Barrier or bridge to effective oncolytic virus therapy?

Oncolytic viruses (OVs) represent a highly promising treatment strategy for a wide range of cancers, by mediating both the direct killing of tumor cells as well as mobilization of antitumor immune responses. As many OVs circulate in the human population, preexisting OV-specific immune responses are prevalent. Indeed, neutralizing antibodies (NAbs) are abundantly present in the human population for commonly used OVs, such as Adenovirus type 5 (Ad5), Herpes Simplex Virus-1 (HSV-1), Vaccinia virus, Measles virus, and Reovirus. This review discusses (pre)clinical evidence regarding the effect of preexisting immunity against OVs on two distinct aspects of OV therapy; OV infection and spread, as well as the immune response induced upon OV therapy. Combined, this review provides evidence that consideration of preexisting immunity is crucial in realizing the full potential of the highly promising therapeutic implementation of OVs. Future investigation of current gaps in knowledge highlighted in this review should yield a more complete understanding of this topic, ultimately allowing for better and more personalized OV therapies.

Dendritic cells and natural killer cells: The road to a successful oncolytic virotherapy

Every type of cancer tissue is theoretically more vulnerable to viral infection. This natural proclivity has been harnessed as a new anti-cancer therapy by employing oncolytic viruses (OVs) to selectively infect and destroy cancer cells while providing little or no harm with no toxicity to the host. Whereas the primary oncolytic capabilities of OVs initially sparked the greatest concern, the predominant focus of research is on the association between OVs and the host immune system. Numerous OVs are potent causal agents of class I MHC pathway-related chemicals, enabling early tumor/viral immune recognition and cytokine-mediated response. The modified OVs have been studied for their ability to bind to dendritic cells (DCs) by expressing growth factors, chemokines, cytokines, and defensins inside the viral genome. OVs, like reovirus, can directly infect DCs, causing them to release chemokines and cytokines that attract and excite natural killer (NK) cells. In addition, OVs can directly alter cancer cells' sensitivity to NK by altering the expression levels of NK cell activators and inhibitors on cancerous cells. Therefore, NK cells and DCs in modulating the therapeutic response should be considered when developing and improving future OV-based therapeutics, whether modified to express transgenes or used in combination with other drugs/immunotherapies. Concerning the close relationship between NK cells and DCs in the potential of OVs to kill tumor cells, we explore how DCs and NK cells in tumor microenvironment affect oncolytic virotherapy and summarize additional information about the interaction mentioned above in detail in this work.

Aptamers Enhance Oncolytic Viruses' Antitumor Efficacy

Oncolytic viruses are highly promising for cancer treatment because they target and lyse tumor cells. These genetically engineered vectors introduce therapeutic or immunostimulatory genes into the tumor. However, viral therapy is not always safe and effective. Several problems are related to oncolytic viruses' targeted delivery to the tumor and immune system neutralization in the bloodstream. Cryoprotection and preventing viral particles from aggregating during storage are other critical issues. Aptamers, short RNA, or DNA oligonucleotides may help to crawl through this bottleneck. They are not immunogenic, are easily synthesized, can be chemically modified, and are not very demanding in storage conditions. It is possible to select an aptamer that specifically binds to any target cell, oncolytic virus, or molecule using the SELEX technology. This review comprehensively highlights the most important research and methodological approaches related to oncolytic viruses and nucleic acid aptamers. Here, we also analyze possible future research directions for combining these two methodologies to improve the effectiveness of cancer virotherapy.

Modern approaches to treating cancer with oncolytic viruses

According to the World Health Organization, cancer is the second leading cause of death in the world. This serves as a powerful incentive to search for new effective cancer treatments. Development of new oncolytic viruses capable of selectively destroying cancer cells is one of the modern approaches to cancer treatment. The advantage of this method – the selective lysis of tumor cells with the help of viruses – leads to an increase in the antitumor immune response of the body, that in turn promotes the destruction of the primary tumor and its metastases. Significant progress in development of this method has been achieved in the last decade. In this review we analyze the literature data on families of oncolytic viruses that have demonstrated a positive therapeutic effect against malignant neoplasms in various localizations. We discuss the main mechanisms of the oncolytic action of viruses and assess their advantages over other methods of cancer therapy as well as the prospects for their use in clinical practice.

The Role of Chemokine IL-7 in Tumor and Its Potential Antitumor Immunity

Interleukin-7 (IL-7) is a cytokine belonging to the chemokine family. It plays a key role in the differentiation, development, and maturation of T lymphocytes and B lymphocytes, which is pivotal to adaptive immunity. In addition to its role in lymphocyte development, recent studies have indicated the antitumor functions of IL-7 in the tumor microenvironment. In this review, we discuss the role of IL-7 in tumors and summarize its antitumor potential and clinical application in lymphoma, leukemia, breast cancer, colon cancer, and so on. Furthermore, the combinational strategies of IL-7 and other antitumor drugs have been also discussed.

Oncolytic Virotherapy in Peritoneal Metastasis Gastric Cancer: The Challenges and Achievements

Gastric cancer (GC) is the fourth most common cancer and the second leading cause of cancer death globally. Although the mortality rate in some parts of the world, such as East Asia, is still high, new treatments and lifestyle changes have effectively reduced deaths from this type of cancer. One of the main challenges of this type of cancer is its late diagnosis and poor prognosis. GC patients are usually diagnosed in the advanced stages of the disease, which is often associated with peritoneal metastasis (PM) and significantly reduces survival. This type of metastasis in patients with GC poses a serious challenge due to limitations in common therapies such as surgery and tumor resection, as well as failure to respond to systemic chemotherapy. To solve this problem, researchers have used virotherapy such as reovirus-based anticancer therapy in patients with GC along with PM who are resistant to current chemotherapies because this therapeutic approach is able to overcome immune suppression by activating dendritic cells (DCs) and eventually lead to the intrinsic activity of antitumor effector T cells. This review summarizes the immunopathogenesis of peritoneal metastasis of gastric cancer (PMGC) and the details for using virotherapy as an effective anticancer treatment approach, as well as its challenges and opportunities.

Eradicating the Roots: Advanced Therapeutic Approaches Targeting Breast Cancer Stem Cells

Accumulating evidences have demonstrated that the existence of breast cancer-initiating cells, which drives the original tumorigenicity, local invasion and migration propensity of breast cancer. These cells, termed as breast cancer stem cells (BCSCs), possess properties including self-renewal, multidirectional differentiation and proliferative potential, and are believed to play important roles in the intrinsic drug resistance of breast cancer. One of the reasons why BCBCs cause difficulties in breast cancer treating is that BCBCs can control both genetic and non-genetic elements to keep their niches safe and sound, which allows BCSCs for constant self-renewal and differentiation. Therapeutic strategies designed to target BCSCs may ultimately result in effective interventions for the treatment of breast cancer. Novel strategies including nanomedicine, oncolytic virus therapy, immunotherapy and induced differentiation therapy are emerging and proved to be efficient in anti-BCSCs therapy. In this review, we summarized breast tumor biology and the current challenges of breast cancer therapies, focused on breast cancer stem cells, and introduced promising therapeutic strategies targeting BCSCs.

Human intratumoral therapy: Linking drug properties and tumor transport of drugs in clinical trials

Cancer therapies aim to kill tumor cells directly or engage the immune system to fight malignancy. Checkpoint inhibitors, oncolytic viruses, cell-based immunotherapies, cytokines, and adjuvants have been applied to prompt the immune system to recognize and attack cancer cells. However, systemic exposure of cancer therapies can induce unwanted adverse events. Intratumoral administration of potent therapies utilizes small amounts of drugs, in an effort to minimize systemic exposure and off-target toxicities. Here, we discuss the properties of the tumor microenvironment and transport considerations for intratumoral drug delivery. Specifically, we consider various tumor tissue factors and physicochemical factors that can affect tumor retention after intratumoral injection. We also review approved and clinical-stage intratumoral therapies and consider how the molecular and biophysical properties (e.g. size and charge) of these therapies influences intratumoral transport (e.g. tumor retention and cellular uptake). Finally, we offer a critical review and highlight several emerging approaches to promote tumor retention and limit systemic exposure of potent intratumoral therapies.

Modeling the Efficacy of Oncolytic Adenoviruses In Vitro and In Vivo: Current and Future Perspectives

Oncolytic adenoviruses (OAd) selectively target and lyse tumor cells and enhance anti- tumor immune responses. OAds have been used as promising cancer gene therapies for many years and there are a multitude of encouraging pre-clinical studies. However, translating OAd therapies to the clinic has had limited success, in part due to the lack of realistic pre-clinical models to rigorously test the efficacy of OAds. Solid tumors have a heterogenous and hostile microenvironment that provides many barriers to OAd treatment, including structural and immunosuppressive components that cannot be modeled in two-dimensional tissue culture. To replicate these characteristics and bridge the gap between pre-clinical and clinical success, studies must test OAd therapy in three-dimensional culture and animal models. This review focuses on current methods to test OAd efficacy in vitro and in vivo and the development of new model systems to test both oncolysis and immune stimulatory components of oncolytic adenovirotherapy.

Attenuated measles vaccine strain have potent oncolytic activity against Iraqi patient derived breast cancer cell line

BACKGROUND

One of the world's leading causes of death among females is breast cancer. Oncolytic viruses are promising anticancer therapy that can overcome resistance to current conventional therapies. Measles virus replicates in and destroys malignant cells without affecting healthy cells. The study aimed to evaluate the lives attenuated Measles virus vaccine against Iraqi patient derived breast cancer cells that have functional BRCA1/BRCA2 genes and compare its activity against international breast cancer MCF-7 and CAL-51 cell lines.

METHODS

The virus was propagated in VERO-hSLAM slam cells. The MTT cytotoxicity assay used to test the virus's ability to kill three human breast cell lines (AMJ13), (MCF-7), and (CAL-51). The cytopathic effect of the measles virus was determined using an H&E stain. Immunocytochemistry assay using specific anti H protein monoclonal antibody for measles virus in the virally infected cells. Finally, apoptosis induction in the infected cells tested using double staining of acridine orange/propidium iodide.

RESULTS

The result shown that breast cancer cells are effectively infected and destroyed by live attenuated measles virus vaccine, and it caused a significant cytopathic effect in the infected cell lines after 48-72 h of infection with remarkable effect on AMJ13 cells (IC50 was 3.527 for AMJ13, when it was 5.079 and 9.171 for MCF-7 and CAL-51 respectively). Measles virus treatment induces apoptosis significantly in breast cancer cell lines compared with control cells.

CONCLUSION

MeV vaccine is useful and safe as anticancer therapy with a notable impact on the local Iraqi breast cancer AMJ13 cells.

Synergistic combination of oncolytic virotherapy with CAR T-cell therapy

For patients with advanced hematological malignancies the therapeutic landscape has been transformed by the emergence of adoptive cell transfer utilizing autologous chimeric antigen receptor (CAR)-redirected T-cells. However, solid tumors have proved far more resistant to this approach. Here, we summarize the numerous challenges faced by CAR T-cells designed to target solid tumors, highlighting, in particular, issues related to impaired trafficking, expansion, and persistence. In parallel, we draw attention to exciting developments in the burgeoning field of oncolytic virotherapy and posit strategies for the synergistic combination of oncolytic viruses with CAR T-cells to improve outcomes for patients with advanced solid tumors.

Talimogene laherparepvec: review of its mechanism of action and clinical efficacy and safety

Intratumoral immunotherapy inhibits tumor growth by killing injected tumor cells, thus initiating local and systemic immune responses. Oncolytic viruses are a novel class of intratumoral immunotherapies that show promise for treating solid tumors. Talimogene laherparepvec is a first-in-class, genetically modified, herpes simplex virus type 1-based oncolytic immunotherapy approved for the local treatment of unresectable cutaneous, subcutaneous and nodal lesions in patients with melanoma recurrent after initial surgery. This review highlights the dual mechanism of action for talimogene laherparepvec (direct tumor cell lysis and stimulation of local response in tumor microenvironment and systemic immune response in distant metastases), summarizes key preclinical and clinical trials evaluating efficacy and safety of talimogene laherparepvec in melanoma, and describes studies ongoing in other solid tumors.

The advent of oncolytic virotherapy in oncology: The Rigvir® story

Oncolytic viruses are a fast-developing cancer treatment field. Numerous viruses have been tested in clinical trials and three are approved. The first, Rigvir, is an immunomodulator with anti-tumour effect for treatment of melanoma, local treatment of skin and subcutaneous metastases of melanoma, for prevention of relapse and metastasis after radical surgery registered in Latvia, Georgia, Armenia and Uzbekistan. The aim of the present review is to summarize the development of Rigvir. Approximately 60 viruses were screened preclinically. Clinical safety and efficacy trials were with 5 oncolytic enteroviruses. Safety of the selected and melanoma-adapted ECHO-7 virus Rigvir was tested in over 180 patients with no severe adverse events observed. Pre-registration efficacy studies involved over 700 cancer patients: over 540 melanoma patients, and patients with late stage stomach (ca. 90), colorectal cancer (ca. 60), and other cancers. Patients were treated with Rigvir for 3 years after surgery and compared to immunotherapy: 3- and 5-year overall survival appeared to be increased in Rigvir treated patients. In post-marketing retrospective studies, Rigvir-treated stage II melanoma patients showed a 6.67-fold decreased risk for disease progression in comparison to those that had been observed according to guidelines, and stage IB and stage II melanoma patients that had received Rigvir therapy had 4.39-6.57-fold lower mortality. The results are confirmed and extended by case reports. Several immunological markers have been measured. In conclusion, Rigvir is an oncotropic and oncolytic virus for treatment of melanoma; the results will be confirmed and updated by modern clinical studies.

Oncolytic Virotherapy versus Cancer Stem Cells: A Review of Approaches and Mechanisms

A growing body of evidence suggests that a subset of cells within tumors are resistant to conventional treatment modalities and may be responsible for disease recurrence. These cells are called cancer stem cells (CSC), which share properties with normal stem cells including self-renewal, pluripotency, drug resistance, and the ability to maintain quiescence. While most conventional therapies can efficiently destroy rapidly dividing cancer cells comprising the bulk of a tumor, they often fail to kill the less abundant and quiescent CSCs. Furthermore, killing of only differentiated cells in the tumor may actually allow for enrichment of CSCs and thereby portend a bad prognosis. Therefore, targeting of CSCs is important to achieve long-term success in cancer therapy. Oncolytic viruses represent a completely different class of therapeutics that can kill cancer cells in a variety of ways, which differ from those of conventional therapies. Hence, CSCs that are inherently resistant to conventional therapies may be susceptible to oncolytic virus-mediated killing. Recent studies have shown that oncolytic viruses can efficiently kill CSCs in many types of cancer. Here, we discuss the mechanism through which CSCs can escape conventional therapies and how they may still be susceptible to different classes of oncolytic viruses. Furthermore, we provide a summary of recent studies that have tested oncolytic viruses on CSCs of different origins and discuss possible future directions for this fascinating subset of oncolytic virus research.

Newcastle disease virus mediates pancreatic tumor rejection via NK cell activation and prevents cancer relapse by prompting adaptive immunity

Pancreatic cancer is the 8th most common cause of cancer-related deaths worldwide and the tumor with the poorest prognosis of all solid malignancies. In 1957, it was discovered that Newcastle disease virus (NDV) has oncolytic properties on tumor cells. To study the oncolytic properties of NDV in pancreatic cancer a single dose was administered intravenously in a syngeneic orthotopic tumor model using two different murine pancreatic adenocarcinoma cell lines (DT6606PDA, Panc02). Tumor growth was monitored and immune response was analyzed. A single treatment with NDV inhibited DT6606PDA tumor growth in mice and prevented recurrence for a period of three months. Tumor infiltration and systemic activation of NK cells, cytotoxic and helper T-cells was enhanced. NDV-induced melting of Panc02 tumors until d7 pi, but they recurred displaying unrestricted tumor growth, low immunogenicity and inhibition of tumor-specific immune response. Arrest of DT6606PDA tumor growth and rejection was mediated by activation of NK cells and a specific antitumor immune response via T-cells. Panc02 tumors rapidly decreased until d7 pi, but henceforth tumors characterized by the ability to perform immune-regulatory functions reappeared. Our results demonstrated that NDV-activated immune cells are able to reject tumors provided that an adaptive antitumor immune response can be initiated. However, activated NK cells that are abundant in Panc02 tumors lead to outgrowth of nonimmunogenic tumor cells with inhibitory properties. Our study emphasizes the importance of an adaptive immune response, which is initiated by NDV to mediate long-term tumor surveillance in addition to direct oncolysis.

Oncolytic Viral Therapy for Mesothelioma

The limited effectiveness of conventional therapy for malignant pleural mesothelioma demands innovative approaches to this difficult disease. Even with aggressive multimodality treatment of surgery, radiation, and/or chemotherapy, the median survival is only 1–2 years depending on stage and histology. Oncolytic viral therapy has emerged in the last several decades as a rapidly advancing field of immunotherapy studied in a wide spectrum of malignancies. Mesothelioma makes an ideal candidate for studying oncolysis given the frequently localized pattern of growth and pleural location providing access to direct intratumoral injection of virus. Therefore, despite being a relatively uncommon disease, the multitude of viral studies for mesothelioma can provide insight for applying such therapy to other malignancies. This article will begin with a review of the general principles of oncolytic therapy focusing on antitumor efficacy, tumor selectivity, and immune system activation. The second half of this review will detail results of preclinical models and human studies for oncolytic virotherapy in mesothelioma.

Oncolytic immunotherapy: unlocking the potential of viruses to help target cancer

Oncolytic immunotherapy is a research area of cancer immunotherapy investigating the use of modified viruses to target cancer cells. A variety of different viral backbones (e.g., adenovirus, reovirus) with a diverse range of genetic modifications are currently being investigated for the treatment of a variety of cancers. The oncolytic virus that has advanced the furthest in clinical development is talimogene laherparepvec, a recombinant HSV-1 virus expressing granulocyte-macrophage colony-stimulating factor (GM-CSF). In a phase 3 study in patients with unresectable metastatic melanoma, intralesional talimogene laherparepvec treatment resulted in a higher durable response rate compared with subcutaneous GM-CSF treatment (16.3 versus 2.1%; P < 0.001). Notably, responses were observed at uninjected lesions including visceral lesions, indicating a systemic antitumor response had occurred. Studies evaluating combination treatments involving oncolytic viruses and immunologic agents are ongoing. This review focuses on the mechanisms of action for oncolytic viruses and highlights select agents and combinations currently in development.

Management of Patients With Skin Cancers: Basal Cell Carcinoma and Melanoma

Novel therapies are changing the treatment paradigm for both melanoma and advanced/metastatic basal cell carcinoma. While immunotherapies are increasing survival benefits in melanoma, they are associated with unique immune-related adverse events.

Viroimmunotherapy for Colorectal Cancer: Clinical Studies

Colorectal cancer is a leading cause of cancer incidence and death. Therapies for those with unresectable or recurrent disease are not considered curative at present. More effective and less toxic therapies are desperately needed. Historically, the immune system was thought to be an enemy to oncolytic viral therapy. Thinking that oncolysis would be the only mechanism for cell death, oncolytic virologists theorized that immune clearance was a detriment to oncolysis. Recent advances in our understanding of the tumor microenvironment, and the interplay of tumor survival and a patient's immune system have called into question our understanding of both arenas. It remains unclear what combination of restrictions or enhancements of innate and/or cell-mediated immunity can yield the highest likelihood of viral efficacy. This article reviews the variety of mechanisms explored for viruses such as immunotherapy for colorectal cancer.

Administration and Handling of Talimogene Laherparepvec: An Intralesional Oncolytic Immunotherapy for Melanoma

PURPOSE/OBJECTIVES

To describe the administration and handling requirements of oncolytic viruses in the context of talimogene laherparepvec (Imlygic™), a first-in-class oncolytic immunotherapy.
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DATA SOURCES

Study procedures employed in clinical trials, in particular the OPTiM study.
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DATA SYNTHESIS

Evaluation of nursing considerations for administration of talimogene laherparepvec.
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CONCLUSIONS

Talimogene laherparepvec is administered through a series of intralesional injections into cutaneous, subcutaneous, or nodal tumors (with ultrasound guidance as needed) during an outpatient clinic visit. A single insertion point is recommended; however, multiple insertion points are acceptable if the tumor radius exceeds the needle's radial reach. Talimogene laherparepvec must be evenly distributed throughout the tumor through each insertion site. Talimogene laherparepvec requires storage at -90°C to -70°C and, once thawed, should be administered immediately or stored in its original vial and carton and protected from light in a refrigerator (2°C to 8°C). 
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IMPLICATIONS FOR NURSING

Because talimogene laherparepvec can be administered in the outpatient setting, nurses will be pivotal for appropriate integration and administration of this unique and effective therapy.

Virotherapy of digestive tumors with rodent parvovirus: overview and perspectives

INTRODUCTION

Toolan's H-1 parvovirus (H-1PV) exerts a cytotoxic/oncolytic effect, predominantly mediated by its non-structural protein (NS1). This rat parvovirus is harmless, unlike other parvoviruses, and its antitumor potential may be useful to clinicians as its oncolytic action appears to be true in numerous non-digestive and digestive cancers.

AREAS COVERED

After a brief review of parvovirus genus and biology, we summarize the proposed mechanisms to explain the cytotoxicity of H-1PV to tumors which results in dysregulation of cell transcription, cell-cycle arrest, termination of cell replication, activation of cellular stress response and induction of cell death. Viral oncolysis induces a strong tumor-specific immune response leading to the recognition and elimination of minimal residual disease. As the action of H-1PV is not limited to the digestive tract, we initially analyse studies performed in non-digestive cancers such as glioma (as the virus is able to cross the blood brain barrier), and then focused more particularly on the results in digestive cancers.

EXPERT OPINION

Based on the results of studies showing little H-1PV toxicity to living bodies, we advocate for the use of the parvovirus in cancers such as melanoma, glioma and pancreatic ductal adenocarcinoma in addition to conventional chemotherapy.

In Vitro Synergistic Enhancement of Newcastle Disease Virus to 5-Fluorouracil Cytotoxicity against Tumor Cells

BACKGROUND

Chemotherapy is one of the antitumor therapies used worldwide in spite of its serious side effects and unsatisfactory results. Many attempts have been made to increase its activity and reduce its toxicity. 5-Fluorouracil (5-FU) is still a widely-used chemotherapeutic agent, especially in combination with other chemotherapies. Combination therapy seems to be the best option for targeting tumor cells by different mechanisms. Virotherapy is a promising agent for fighting cancer because of its safety and selectivity. Newcastle disease virus is safe, and it selectively targets tumor cells. We previously demonstrated that Newcastle disease virus (NDV) could be used to augment other chemotherapeutic agents and reduce their toxicity by halving the administered dose and replacing the eliminated chemotherapeutic agents with the Newcastle disease virus; the same antitumor activity was maintained.

METHODS

In the current work, we tested this hypothesis on different tumor cell lines. We used the non-virulent LaSota strain of NDV in combination with 5-FU, and we measured the cytotoxicity effect. We evaluated this combination using Chou-Talalay analysis.

RESULTS

NDV was synergistic with 5-FU at low doses when used as a combination therapy on different cancer cells, and there were very mild effects on non-cancer cells.

CONCLUSION

The combination of a virulent, non-pathogenic NDV-LaSota strain with a standard chemotherapeutic agent, 5-FU, has a synergistic effect on different tumor cells in vitro, suggesting this combination could be an important new adjuvant therapy for treating cancer.

Dendritic Cells in Oncolytic Virus-Based Anti-Cancer Therapy

Dendritic cells (DCs) are specialized antigen-presenting cells that have a notable role in the initiation and regulation of innate and adaptive immune responses. In the context of cancer, appropriately activated DCs can induce anti-tumor immunity by activating innate immune cells and tumor-specific lymphocytes that target cancer cells. However, the tumor microenvironment (TME) imposes different mechanisms that facilitate the impairment of DC functions, such as inefficient antigen presentation or polarization into immunosuppressive DCs. These tumor-associated DCs thus fail to initiate tumor-specific immunity, and indirectly support tumor progression. Hence, there is increasing interest in identifying interventions that can overturn DC impairment within the TME. Many reports thus far have studied oncolytic viruses (OVs), viruses that preferentially target and kill cancer cells, for their capacity to enhance DC-mediated anti-tumor effects. Herein, we describe the general characteristics of DCs, focusing on their role in innate and adaptive immunity in the context of the TME. We also examine how DC-OV interaction affects DC recruitment, OV delivery, and anti-tumor immunity activation. Understanding these roles of DCs in the TME and OV infection is critical in devising strategies to further harness the anti-tumor effects of both DCs and OVs, ultimately enhancing the efficacy of OV-based oncotherapy.

Metastatic melanoma treatment: Combining old and new therapies

Metastatic melanoma is an aggressive form of cancer characterised by poor prognosis and a complex etiology. Until 2010, the treatment options for metastatic melanoma were very limited. Largely ineffective dacarbazine, temozolamide or fotemustine were the only agents in use for 35 years. In recent years, the development of molecularly targeted inhibitors in parallel with the development of checkpoint inhibition immunotherapies has rapidly improved the outcomes for metastatic melanoma patients. Despite these new therapies showing initial promise; resistance and poor duration of response have limited their effectiveness as monotherapies. Here we provide an overview of the history of melanoma treatment, as well as the current treatments in development. We also discuss the future of melanoma treatment as we go beyond monotherapies to a combinatorial approach. Combining older therapies with the new molecular and immunotherapies will be the most promising way forward for treatment of metastatic melanoma.

Oncolytic Replication of E1b-Deleted Adenoviruses

Various viruses have been studied and developed for oncolytic virotherapies. In virotherapy, a relatively small amount of viruses used in an intratumoral injection preferentially replicate in and lyse cancer cells, leading to the release of amplified viral particles that spread the infection to the surrounding tumor cells and reduce the tumor mass. Adenoviruses (Ads) are most commonly used for oncolytic virotherapy due to their infection efficacy, high titer production, safety, easy genetic modification, and well-studied replication characteristics. Ads with deletion of E1b55K preferentially replicate in and destroy cancer cells and have been used in multiple clinical trials. H101, one of the E1b55K-deleted Ads, has been used for the treatment of late-stage cancers as the first approved virotherapy agent. However, the mechanism of selective replication of E1b-deleted Ads in cancer cells is still not well characterized. This review will focus on three potential molecular mechanisms of oncolytic replication of E1b55K-deleted Ads. These mechanisms are based upon the functions of the viral E1B55K protein that are associated with p53 inhibition, late viral mRNA export, and cell cycle disruption.

Oncolytic adenovirus targeting cyclin E overexpression repressed tumor growth in syngeneic immunocompetent mice

Background

Clinical trials have indicated that preclinical results obtained with human tumor xenografts in mouse models may overstate the potential of adenovirus (Ad)-mediated oncolytic therapies. We have previously demonstrated that the replication of human Ads depends on cyclin E dysregulation or overexpression in cancer cells. ED-1 cell derived from mouse lung adenocarcinomas triggered by transgenic overexpression of human cyclin E may be applied to investigate the antitumor efficacy of oncolytic Ads.

Methods

Ad-cycE was used to target cyclin E overexpression in ED-1 cells and repress tumor growth in a syngeneic mouse model for investigation of oncolytic virotherapies.

Results

Murine ED-1 cells were permissive for human Ad replication and Ad-cycE repressed ED-1 tumor growth in immunocompetent FVB mice. ED-1 cells destroyed by oncolytic Ads in tumors were encircled in capsule-like structures, while cells outside the capsules were not infected and survived the treatment.

Conclusion

Ad-cycE can target cyclin E overexpression in cancer cells and repress tumor growth in syngeneic mouse models. The capsule structures formed after Ad intratumoral injection may prevent viral particles from spreading to the entire tumor.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1731-x) contains supplementary material, which is available to authorized users.

Adapted ECHO-7 virus Rigvir immunotherapy (oncolytic virotherapy) prolongs survival in melanoma patients after surgical excision of the tumour in a retrospective study

An oncolytic, nonpathogenic ECHO-7 virus adapted for melanoma that has not been genetically modified (Rigvir) is approved and registered for virotherapy, an active and specific immunotherapy, in Latvia since 2004. The present retrospective study was carried out to determine the effectiveness of Rigvir in substage IB, IIA, IIB and IIC melanoma patients on time to progression and overall survival. White patients (N=79) who had undergone surgical excision of the primary melanoma tumour were included in this study. All patients were free from disease after surgery and classified into substages IB, IIA, IIB and IIC. Circulating levels of clinical chemistry parameters were recorded. Survival was analysed by Cox regression. Rigvir significantly (P<0.05) prolonged survival in substage IB-IIC melanoma patients following surgery compared with patients who were under observation (according to current guidelines). The hazard ratio for patients under observation versus treated with Rigvir was statistically significantly different: hazard ratio 6.27 for all, 4.39 for substage IIA-IIB-IIC and 6.57 for substage IIB-IIC patients. The follow-up period was not statistically different between both treatment groups. These results indicate that the patients treated with Rigvir had a 4.39-6.57-fold lower mortality than those under observation. In this study, there was no untoward side effect or discontinuation of Rigvir treatment. Safety assessment of adverse events graded according to NCI CTCAE did not show any value above grade 2 in Rigvir-treated patients. In conclusion, Rigvir significantly prolongs survival in early-stage melanoma patients without any side effect.

Utilizing the BiTE (bispecific T-cell engager) platform for immunotherapy of cancer

Various approaches of T-cell-based cancer immunotherapy are currently under investigation, among these are BiTE® (bispecific T-cell engager) antibody constructs, which have a unique design and mechanism of action. They are constructed by genetically linking onto a single polypeptide chain the minimal binding domains of monoclonal antibodies for tumor-associated surface antigens and for the T-cell receptor-associated molecule CD3. Concurrent engagement of the target cell antigen and CD3 leads to activation of polyclonal cytotoxic T-cells, resulting in target cell lysis. Blinatumomab, a BiTE targeting CD19, is being investigated in a broad range of B-cell malignancies and has recently been approved in the USA by the US FDA for Philadelphia chromosome-negative relapsed/refractory B-acute lymphoblastic leukemia under the trade name BLINCYTO™. The BiTE platform is one of the clinically most advanced T-cell immunotherapy options.

Synthetic immunosurveillance systems: nanodevices to monitor physiological events

The field of nanotechnology has recently seen vast advancements in its applications for therapeutic strategy. This technological revolution has led way to nanomedicine, which spurred the development of clever drug delivery designs and ingenious nanovehicles for the monitoring of cellular events in vivo. The clinical implementations of this technology are innumerable and have demonstrated utility as diagnostic tools and fortifying machineries for the mammalian immune system. Recently engineered viral vectors and multi-subunit packaging RNAs have verified stable enough for long-term existence in the physiological environment and therefore reveal unique potential as artificial immunosurveillance devices. Physiological and pathological events recorded by nanodevices could help develop "biocatalogs" of patients' infection history, frequency of disease, and much more. In this article, we introduce a novel design concept for a multilayer synthetic immune network parallel to the natural immune system; an artificial network of continuously patrolling nanodevices incorporated in the blood and lymphatic systems, and adapted for molecular event recording, anomaly detection, drug delivery, and gene silencing. We also aim to discuss the approaches and advances recently reported in nanomedicine, especially as it pertains to promising viral and RNA-based nanovehicles and their prospective applications for the development of a synthetic immunosurveillance system (SIS). Alternative suggestions and limitations of these technologies are also discussed.

Virotherapy targeting cyclin E overexpression in tumors with adenovirus-enhanced cancer-selective promoter

Oncolytic virotherapy can selectively destroy cancer cells and is a potential approach in cancer treatment. A strategy to increase tumor-specific selectivity is to control the expression of a key regulatory viral gene with a tumor-specific promoter. We have previously found that cyclin E expression is augmented in cancer cells after adenovirus (Ad) infection. Thus, the cyclin E promoter that is further activated by Ad in cancer cells may have unique properties for enhancing oncolytic viral replication. We have shown that high levels of viral E1a gene expression are achieved in cancer cells infected with Ad-cycE, in which the endogenous Ad E1a promoter was replaced with the cyclin E promoter. Ad-cycE shows markedly selective oncolytic efficacy in vitro and destroys various types of cancer cells, including those resistant to ONYX-015/dl1520. Furthermore, Ad-cycE shows a strong capacity to repress A549 xenograft tumor growth in nude mice and significantly prolongs survival. This study suggests the potential of Ad-cycE in cancer therapy and indicates the advantages of using promoters that can be upregulated by virus infection in cancer cells in development of oncolytic viruses. Key messages: Cyclin E promoter activity is high in cancer cells and enhanced by adenovirus infection. Cyclin E promoter is used to control the E1a gene of a tumor-specific oncolytic adenovirus. Ad-cycE efficiently targets cancer cells and induces oncolysis. Ad-cycE significantly repressed xenograft tumor and prolonged survival.

Oncolytic viruses in head and neck cancer: a new ray of hope in the management protocol

This paper intends to highlight the different types of oncolytic viruses (OVs), mechanism of tumor specificity, its safety, and various obstacles in the design of treatment and combination therapy utilizing oncotherapy. Search was conducted using the internet-based search engines and scholarly bibliographic databases with key words such as OVs, head and neck cancer, viruses, oral squamous cell carcinoma, and gene therapy. Revolutionary technologies in the field of cancer treatment have gone through a series changes leading to the development of innovative therapeutic strategies. Oncolytic virotherapy is one such therapeutic approach that has awaited phase III clinical trial validation. OVs are self-replicating, tumor selective and lyse cancer cells following viral infection. By modifying the viral genome, it is possible to direct their toxicity toward cancer cells. Viruses that are used for treatment of head and neck cancer are either naturally occurring or genetically modified. OVs are tumor selective and potential anticancer agents. Virotherapy may become the standard of care and part of combination therapy in the management of head and neck cancer in the future.

Molecular imaging with bioluminescence and PET reveals viral oncolysis kinetics and tumor viability

Viral oncolysis, the destruction of cancer cells by replicating virus, is an experimental cancer therapy that continues to be explored. The treatment paradigm for this therapy involves successive waves of lytic replication in cancer cells. At present, monitoring viral titer at sites of replication requires biopsy. However, repeat serial biopsies are not practically feasible for temporal monitoring of viral replication and tumor response in patients. Molecular imaging provides a noninvasive method to identify intracellular viral gene expression in real time. We imaged viral oncolysis and tumor response to oncolysis sequentially with bioluminescence and positron emission tomography (PET), revealing the kinetics of both processes in tumor xenografts. We demonstrate that virus replication cycles can be identified as successive waves of reporter expression that occur ∼2 days after the initial viral tumor infection peak. These waves correspond to virions that are released following a replication cycle. The viral and cellular kinetics were imaged with Fluc and Rluc bioluminescence reporters plus two 18F-labeled PET reporters FHBG [9-(4-18F-fluoro-3-[hydroxymethyl] butyl) guanine] and FLT (18F-3'-deoxy-3-'fluorothymidine), respectively. Correlative immunohistochemistry on tumor xenograft sections confirmed in vivo results. Our findings show how PET can be used to identify virus replication cycles and for real-time measurements of intratumoral replicating virus levels. This noninvasive imaging approach has potential utility for monitoring viral oncolysis therapy in patients.

Methods for gene transfer to the central nervous system

Gene transfer is an increasingly utilized approach for research and clinical applications involving the central nervous system (CNS). Vectors for gene transfer can be as simple as an unmodified plasmid, but more commonly involve complex modifications to viruses to make them suitable gene delivery vehicles. This chapter will explain how tools for CNS gene transfer have been derived from naturally occurring viruses. The current capabilities of plasmid, retroviral, adeno-associated virus, adenovirus, and herpes simplex virus vectors for CNS gene delivery will be described. These include both focal and global CNS gene transfer strategies, with short- or long-term gene expression. As is described in this chapter, an important aspect of any vector is the cis-acting regulatory elements incorporated into the vector genome that control when, where, and how the transgene is expressed.

Histone deacetylase inhibitors potentiate vesicular stomatitis virus oncolysis in prostate cancer cells by modulating NF-κB-dependent autophagy

Vesicular stomatitis virus (VSV) is an oncolytic virus that induces cancer cell death through activation of the apoptotic pathway. Intrinsic resistance to oncolysis is found in some cell lines and many primary tumors as a consequence of residual innate immunity to VSV. In resistant-tumor models, VSV oncolytic potential can be reversibly stimulated by combination with epigenetic modulators, such as the histone deacetylase inhibitor vorinostat. Based on this reversible effect of vorinostat, we reasoned that critical host genes involved in oncolysis may likewise be reversibly regulated by vorinostat. A transcriptome analysis in prostate cancer PC3 cells identified a subset of NF-κB target genes reversibly regulated by vorinostat, as well as a group of interferon (IFN)-stimulated genes (ISGs). Consistent with the induction of NF-κB target genes, vorinostat-mediated enhancement of VSV oncolysis increased hyperacetylation of NF-κB RELA/p65. Additional bioinformatics analysis revealed that NF-κB signaling also increased the expression of several autophagy-related genes. Kinetically, autophagy preceded apoptosis, and apoptosis was observed only when cells were treated with both VSV and vorinostat. VSV replication and cell killing were suppressed when NF-κB signaling was inhibited using pharmacological or genetic approaches. Inhibition of autophagy by 3-methyladenine (3-MA) enhanced expression of ISGs, and either 3-MA treatment or genetic ablation of the autophagic marker Atg5 decreased VSV replication and oncolysis. Together, these data demonstrate that vorinostat stimulates NF-κB activity in a reversible manner via modulation of RELA/p65 signaling, leading to induction of autophagy, suppression of the IFN-mediated response, and subsequent enhancement of VSV replication and apoptosis.

Intralesional immunotherapy for melanoma

Intralesional immunotherapy of melanoma has two complementary aims. One is to cause regression of the injected metastasis. The other is to incite or modulate systemic immune responses in such a way that non-injected metastases will also undergo regression. A number of phase 1 and phase II studies with cytokines, viral, or bacterial agents have been conducted but their use has remained sporadic and has not progressed to become established treatments. Two treatments have progressed to randomized phase III studies. The most promising of these is based on intralesional injection of a genetically modified herpes simplex virus (HSV) (T-Vec). Initial results have shown a significant effect on durable response rates (DRR) but effects on overall survival remain under study. The second involved injection of plasmids coding for the HLA B7 antigen (Allovectin). Despite encouraging early results the treatment did not reach its endpoints and its use has been discontinued. A phase II study involving intralesional injection of oncolytic A21 coxsackie virus (Cavatak) is also under way and is showing promise.

Therapeutic strategies in the management of patients with metastatic anaplastic thyroid cancer: review of the current literature

PURPOSE OF REVIEW

Anaplastic thyroid cancer (ATC) is a rare and deadly malignancy. There is a need to speed up and support clinical research. This review article focuses on the new molecules that have been developed for the treatment of this aggressive tumor.

RECENT FINDINGS

Improvement in the knowledge of pathogenesis and genetics of ATC led to the development of a variety of new molecules that may be used to treat this disease. In summary, these molecules are proteasome inhibitors, Aurora kinase inhibitors, vascular targeting agents, and gene therapies. All these molecules demonstrated a potentially therapeutic activity in metastatic ATC. To date, the largest prospective randomized multicenter, open-label, trial was conducted with combretastatin-A4.

SUMMARY

More efficient drugs need to be developed through multinational efforts.

Oncolytic vaccinia virus therapy of salivary gland carcinoma

OBJECTIVE

To examine the therapeutic effects of an attenuated, replication-competent vaccinia virus (GLV-1h68) against a panel of 5 human salivary gland carcinoma cell lines.

DESIGN

The susceptibility of 5 salivary gland carcinoma cell lines to infection and oncolysis by GLV-1h68 was assessed in vitro and in vivo.

RESULTS

All 5 cell lines were susceptible to viral infection, transgene expression, and cytotoxic reactions. Three cell lines were exquisitely sensitive to infection by very low doses of GLV-1h68. Orthotopic parotid tumors exhibited more aggressive behavior compared with flank tumors. A single intratumoral injection of GLV-1h68 induced significant tumor regression without observed toxic effects in flank and parotid tumor models; controls demonstrated rapid tumor progression.

CONCLUSION

These promising results demonstrate significant oncolytic activity by an attenuated vaccinia virus for infecting and lysing salivary gland carcinomas, supporting future clinical trials.

Investigation of cytotoxicity of negative control peptides versus bioactive peptides on skin cancer and normal cells: a comparative study

BACKGROUND

Resonant recognition model-myxoma virus (RRM-MV), a bioactive peptide analogue for myxoma virus MV-T5 protein, was computationally designed by the RRM. In this study, the anticancer effects of RRM-MV were assessed in vitro against four negative control peptides on human skin cancer and normal cells.

RESULTS & DISCUSSION

The effects of RRM-MV versus negative control peptides on cells were evaluated by quantitative and qualitative assays. The RRM-MV treatment was able to induce cell death in cancer cells without triggering similar effects on normal cells. However, the negative control peptides produced no toxic effects on skin cancer and normal cells. No effects on human erythrocytes were detected when treated with all peptides.

CONCLUSION

It is suggested that the RRM can be applied to design therapeutic anticancer peptides.

Preclinical efficacy of the oncolytic measles virus expressing the sodium iodide symporter in iodine non-avid anaplastic thyroid cancer: a novel therapeutic agent allowing noninvasive imaging and radioiodine therapy

Anaplastic thyroid cancer is an extremely aggressive disease resistant to radioiodine treatment because of loss of sodium iodide symporter (NIS) expression. To enhance prognosis of this fatal cancer, we validated the preclinical efficacy of measles virus (MV)-NIS, the vaccine strain of the oncolytic MV (MV-Edm), modified to include the NIS gene. Western blotting analysis confirmed that a panel of eight anaplastic thyroid cancer (ATC)-derived cell lines do not express NIS protein, but do express CD46, the MV receptor. In vitro cell death assays and in vivo xenograft studies demonstrate the oncolytic efficacy of MV-NIS in BHT-101 and KTC-3, ATC-derived cell lines. Radioactive iodine uptake along with single-photon emission computed tomography (SPECT)-computed tomography imaging of KTC-3 xenografts after (99)Tc(m) administration confirmed NIS expression in vitro and in vivo, respectively, after virus treatment. Adjuvant administration of RAI, to MV-NIS-treated KTC-3 tumors showed a trend for increased tumor cell killing. As current treatment for ATC is only palliative, and MV-NIS is currently Food and Drug Administration approved for human clinical trials in myeloma, our data indicate that targeting ATC with MV-NIS could prove to be a novel therapeutic strategy for effective treatment of iodine-resistant ATC and will expedite its testing in clinical trials for this aggressive disease.

Cytolytic replication of echoviruses in colon cancer cell lines

BACKGROUND

Colorectal cancer is one of the most common cancers in the world, killing nearly 50% of patients afflicted. Though progress is being made within surgery and other complementary treatments, there is still need for new and more effective treatments. Oncolytic virotherapy, meaning that a cancer is cured by viral infection, is a promising field for finding new and improved treatments. We have investigated the oncolytic potential of several low-pathogenic echoviruses with rare clinical occurrence. Echoviruses are members of the enterovirus genus within the family Picornaviridae.

METHODS

Six colon cancer cell lines (CaCo-2, HT29, LoVo, SW480, SW620 and T84) were infected by the human enterovirus B species echovirus 12, 15, 17, 26 and 29, and cytopathic effects as well as viral replication efficacy were investigated. Infectivity was also tested in spheroids grown from HT29 cells.

RESULTS

Echovirus 12, 17, 26 and 29 replicated efficiently in almost all cell lines and were considered highly cytolytic. The infectivity of these four viruses was further evaluated in artificial tumors (spheroids), where it was found that echovirus 12, 17 and 26 easily infected the spheroids.

CONCLUSIONS

We have found that echovirus 12, 17 and 26 have potential as oncolytic agents against colon cancer, by comparing the cytolytic capacity of five low-pathogenic echoviruses in six colon cancer cell lines and in artificial tumors.

Transarterial injection of H101 in combination with chemoembolization overcomes recurrent hepatocellular carcinoma

Transcatheter arterial chemoembolization (TACE) has become the standard treatment modality for unresectable hepatocellular carcinoma (HCC). Nonetheless, the clinical outcomes in patients with unresectable HCC are often unsatisfactory, especially in those with recurrent HCC. H101, an E1B gene deleted adenovirus, is known to have a significant antitumor activity. In addition, local injection of H101 can enhance the effect of antitumor therapies (chemotherapy and radiotherapy). Transarterial H101 gene injection in combination with TACE may help to control refractory and recurrent HCC. In this study, we report a 55-year-old patient with recurrent HCC which was treated with transarterial injection of H101 in combination with TACE, leading to a good clinical prognosis of the patient.

Therapeutic effects of a fusogenic newcastle disease virus in treating head and neck cancer

BACKGROUND

Newcastle disease virus (NDV) is a paramyxovirus that is pathogenic in birds but causes only mild flulike symptoms in human beings. NDV(F3aa)-GFP is a genetically modified, fusogenic NDV. We assessed the utility of NDV(F3aa)-GFP in treating head and neck squamous cell carcinoma.

METHODS AND RESULTS

At a multiplicity of infection (MOI) of 1, NDV(F3aa)-GFP infection of 3 cell lines supported strong GFP expression by 36 hours. Four cell lines were highly sensitivite to viral cytotoxicity, with >75% of cells lysed by day 6 at MOI 0.1, and 2 other cell lines were partially susceptible. Murine SCC25 flank tumors exhibited robust GFP expression after a single intratumoral viral injection and showed near-complete tumor regression over 34 days. There were no adverse effects attributable to therapy.

CONCLUSIONS

We demonstrate that a fusogenic NDV exerts potent oncolytic effects against human head and neck cancer and support its continued investigation for clinical application.

HSV as a vector in vaccine development and gene therapy

The very deep knowledge acquired on the genetics and molecular biology of herpes simplex virus (HSV), major human pathogen whose lifestyle is based on a long-term dual interaction with the infected host characterized by the existence of lytic and latent infections, has allowed the development of potential vectors for several applications in human healthcare. These include delivery and expression of human genes to cells of the nervous system, selective destruction of cancer cells, prophylaxis against infection with HSV or other infectious diseases and targeted infection of specific tissues or organs. Three different classes of vectors can be derived from HSV-1: replication-competent attenuated vectors, replication-incompetent recombinant vectors and defective helper-dependent vectors known as amplicons. This chapter highlights the current knowledge concerning design, construction and recent applications, as well as the potential and current limitations of the three different classes of HSV-1-based vectors.

HSV Recombinant Vectors for Gene Therapy

The very deep knowledge acquired on the genetics and molecular biology of herpes simplex virus (HSV), has allowed the development of potential replication-competent and replication-defective vectors for several applications in human healthcare. These include delivery and expression of human genes to cells of the nervous systems, selective destruction of cancer cells, prophylaxis against infection with HSV or other infectious diseases, and targeted infection to specific tissues or organs. Replication-defective recombinant vectors are non-toxic gene transfer tools that preserve most of the neurotropic features of wild type HSV-1, particularly the ability to express genes after having established latent infections, and are thus proficient candidates for therapeutic gene transfer settings in neurons. A replication-defective HSV vector for the treatment of pain has recently entered in phase 1 clinical trial. Replication-competent (oncolytic) vectors are becoming a suitable and powerful tool to eradicate brain tumours due to their ability to replicate and spread only within the tumour mass, and have reached phase II/III clinical trials in some cases. The progress in understanding the host immune response induced by the vector is also improving the use of HSV as a vaccine vector against both HSV infection and other pathogens. This review briefly summarizes the obstacle encountered in the delivery of HSV vectors and examines the various strategies developed or proposed to overcome such challenges.